Shinsuke Udagawa

Interferometric signal measurement of shock waves and contact surfaces in small scale shock tube

In this study we have performed the experiment under the several pressure conditions by using the mini-shock tube of 3mm diameter, which was developed by Garen, by using the interferometric signal measurement with the collimated and polarized laser beams. It is confirmed that the shock waves do not propagate at constant velocity in this mini-shock tube. We have also performed a numerical simulation by using two-dimensional and axi-symmetric N-S equation to compare with the experimental results. The experimental results are shown with the numerical results on the x-t diagram. It is confirmed that the influence of the friction between the test gas and the wall produces the difference between the inclinations of x - t curves of the diagram.

Shock waves in mini-tubes: influence of the scaling parameter S

Weak shock waves have been investigated in a glass tube of 1 mm diameter and a length of 600 mm. The distance between shock and contact surface is approximately 10 mm and both travel nearly with the same speed at the measuring position of 410 mm. For a laminar flow behind the shock wave an identical Mach number M 1 can be generated with two different shock strength values p 41 as a consequence of friction effects.

Interferometric Measurement in Shock Tube Experiments

This chapter describes applications of interferometry to the shock tube experiments. The first topic is Laser Interferometric Computed Tomography (LICT) technique to realize the three-dimensional (3D) density measurement of high-speed and unsteady flow field behind shock waves discharging from nozzles. The second topic is measurement of propagating shock wave in micro-scale shock tube by interferometic approach. Micro-scale shock tube is being researched in several fields of science recently and micro-scale shock wave has possibilities of applications for various fields medical, engineering, ...etc. Clarifying the characteristics of micro-scale shock tube to generate the micro-scale shock wave is very important step for the application.

Propagation of the shock wave generated by two-dimensional beam focusing of a CO2 pulsed laser

To simulate the field for the actual scale explosion experiments is sometimes very difficult. From the reasons of safety-space, schedules, and human factor the number of actual field explosion experiments has been strictly limited. Therefore a small scale shock wave generator is considered to be very useful for experimentally simulating the explosion phenomena[1]. This study deals with the blast effects by using laser -induced micro shock wave. A plasma and a shock wave, which generated by a focusing pulsed CO2 laser beam into a two-dimensional acrylic resin structure model by a cylindrical lens, have been visualized by the schlieren method. Moreover, the numerical simulation for compressible and inviscid flow with thermal equilibrium has been conducted to clarify the propagation characteristics of the laser induced shock wave.

Decomposition experiment of hydro-fluorocarbon gas by pulsed TEA CO2 laser

This paper deals with a trial experiment of decomposition of environmental gas R-12 by the pulsed TEA CO2 laser. Nowadays refrigerant R-12 and other hydro-chlorofluorocarbon gases are strongly prohibited to produce, as these gases have both strong ozone-depleting effects and green-house effects. The gases of already produced by huge amount should be decomposed as fast as possible by suitable technical methods. Along with the conventional kiln furnace of cement, arc discharge and the HG discharge are good methods for the freon decomposition. Both methods, however, have the weakness of electrode damages (arcing) or low-pressure operation (HF discharge). High power CO2 laser seems to have good properties for such decomposition with favorable wavelength for the absorption. In our small-scale experiment of gas decomposition a pulsed TEA CO2 laser of several joules is utilized to produce the plasma in R-12 flow channel of glass tube. The withdrawal of decomposed gases is performed by Ca alkalized water. The deposit mass is measured, and powder X-ray diffraction measurement is carried out on the deposit powder. The possibility of our laser gas decomposition is discussed.

Hybrid algebraic reconstruction technique for tomographic reconstruction of the wave interaction around a rectangular rod

Laser Interferometric Computed Tomography (LICT) measurement enabled observation of the three-dimensional (3-D) density distribution of the unsteady flow field quantitatively. The interferometric fringe images are used as the projection data, and the flow field is reconstructed by appropriate reconstruction technique in LICT measurement. The flow field which do not include any object is reconstructed clearly. On the other hand, if the obstacle is included in the flow field, laser beam cannot pass through the obstacle and the projection data have imperfect parts. These imperfect parts cause strong artifacts in the CT images and we cannot identify any unsteady phenomena. To reduce these artifacts, we applied Hybrid Algebraic Reconstruction Technique (HART). In this study, the HART technique will be applied to the problem of reconstruction of wave interaction around a rectangular rod, and CT images obtained using HART and Algebraic Reconstruction Technique (ART) will be compared.Graphical Abstract

Study on Si Wafer Cooling by Low Pressure Argon Gas in Vacuum Eenvironment

The circuit line width of DRAM has been matched 45nm design rule at half pitch in 2010 by the ITRS 2005[1]. The laser or low energy electoron beam as next generation lithography exposure beam source has high energy, and the local and thermal deformation by the energy causes the pattern placement error. Therefore, decreasing the deformation is key issue. In this paper, we have performed the experiment with silicon wafer and argon gas by using experimental apparatus[2]. We also calculate the thermal accommodation coefficient between argon gas and silicon wafer by using our experimental results and FEM solutions.